1. Field of the Invention
The invention relates to a method for performing a contrast vision test in a subject in order to determine a contrast sensitivity function. The invention likewise relates to a computer program for performing the method, and also to a computer program product and a computer for executing the computer program.
2. Description of the Related Art
In contrast vision tests, a subject's ability to see contrasts is determined with the aid of a contrast sensitivity function. This is done in the case of previous appliances and measurement methods by measuring discrete visual acuity and contrast values. Suitable measurement objects used here are, as known for example from U.S. Pat. No. 5,500,699, Landolt rings and also letters of different sizes with specific discrete contrast values. In addition, sinusoidal gratings having a specific fixed frequency, i.e. spatial frequency, and a specific contrast value are sometimes used.
Tests of this kind have been used hitherto only for partially sighted persons or to diagnose pathological changes in the visual apparatus. The evaluation is usually carried out by registering the discrete points in a visual acuity/contrast scheme and visually comparing various registered data items.
The individual contrast sensitivity function can provide information on the eyesight or on eyesight problems even in normally ametropic persons. The discrete gradations of the known contrast vision tests are, however, too crude for this group of persons. Previous tests furthermore do not cover the entire contrast and visual acuity range applicable to normally ametropic persons. The previous evaluation methods also involve the problem that no continuous data which would enable automatic further processing is digitally registered.
Furthermore, no meaningful metric which can be used to describe the contrast sensitivity function exists as yet.
The present invention is therefore based on the object of providing a method of the kind mentioned in the introduction, which avoids the disadvantages of the prior art and in particular makes available a meaningful contrast vision test for determining a contrast sensitivity function even in normally ametropic subjects.